The purpose of this contract is to complete the work started under a subcontract to Tracor Jitco for 15 chemicals (Propylene oxide, methyl methacrylate, propylene, 1,2-epoxybutane, ethylene oxide, tetrachloroethlene, methylene chloride, 1,3-butadiene, ethyl bromidean chloride, formaldehyde, Alpha-chloroacetophenone, O-chlorobenzolnalonitrite, allyl glycidyl ether, and epinephrine. The objective of this project is to characterize dose-response relationships and toxicity of chemicals administered by inhalation to male and female rats and mice in prechronic and 2-year chronic studies. Animals will be exposed for 6 hours per day, 5 days per week for 14 days or 13 and 104 weeks. At the end of each study, all animals will be given gross and microscopic histopathologic evaluations. The results of each study will be used by NTP to establish doses to be used in the next study. The results of the 2-year chronic study will be used by NTP to determine toxicologic and carcinogenic effects of inhalation administration of these chemicals.